We have been investigating the role of prolactin in breast and prostate cancer and simultaneously evaluating the effects of prolactin and other hormones on normal breast and prostate tissue. We have developed a sensitive and specific radioimmunoassay for human alpha-lactalbumin which is capable of measuring small quantities of alpha-lactalbumin in serum, tissue homogenates and organ culture medium. We have been utilizing the measurement of this milk protein and others to determine the effect of prolactin on breast tissue. BIBLIOGRAPHIC REFERENCES: Kleinberg, D.L., Todd, J. and Niemann, W. Effect of Prolactin on alpha-lactalbumin in Normal Human and Primate Breast. Clin. Res. May, 1976 (Abstract in Press). Kleinberg, D.L. and Frantz, A.G. Effects on alpha-lactalbumin and Prolactin of CB-154 Treatment for Galactorrhea. Proceedings of the Endocrine Society. June, 1976 (Abstract in Press).